890-million-year old sponge fossils may be earliest animal

FOSSILISED structures discovered in northwestern Canada may be from sponges that lived in oceans as long as 890 million years ago, making them the earliest known animal life on Earth, new research suggests.

The findings challenge the idea that animals did not begin on Earth before an infusion of oxygen into the atmosphere and oceans. Genetic tests on modern sponges show they emerged a billion to 500 million years ago but until now there has been no evidence of fossilised sponge bodies from this period, the early Neoproterozoic era.

Prof Elizabeth Turner of Canada’s Laurentian University looked for evidence of sponges in 890-millionyear-old reefs constructed by a bacteria that deposited calcium carbonate.

She found networks of tiny tubeshaped structures containing crystals of the mineral calcite – suggesting they were contemporaneous to the reef – that resemble the fibrous skeleton found within some modern sponges.

If the structures are verified as sponge samples, they will outdate the current oldest known sponge fossils by 350 million years, says the report published in the journal Nature. Prof Turner said: “The earliest animals to emerge evolutionarily were probably sponge-like. This too is not surprising, given that sponges are the most basic animal in the tree of life.”

If the structures do turn out to be confirmed as sponge specimens, that means they would have lived roughly 90 million years before Earth’s oxygen levels reached levels thought to be necessary to support animal life.